arch/arm/common/dmabounce.c - LeafOS-Devices/android_kernel_samsung_universal7904 - Gitiles

 /*
  *  arch/arm/common/dmabounce.c
  *
  *  Special dma_{map/unmap/dma_sync}_* routines for systems that have
  *  limited DMA windows. These functions utilize bounce buffers to
  *  copy data to/from buffers located outside the DMA region. This
  *  only works for systems in which DMA memory is at the bottom of
  *  RAM and the remainder of memory is at the top an the DMA memory
  *  can be marked as ZONE_DMA. Anything beyond that such as discontigous
  *  DMA windows will require custom implementations that reserve memory
  *  areas at early bootup.
  *
  *  Original version by Brad Parker (brad@heeltoe.com)
  *  Re-written by Christopher Hoover <ch@murgatroid.com>
  *  Made generic by Deepak Saxena <dsaxena@plexity.net>
  *
  *  Copyright (C) 2002 Hewlett Packard Company.
  *  Copyright (C) 2004 MontaVista Software, Inc.
  *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  version 2 as published by the Free Software Foundation.
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmapool.h>
 #include <linux/list.h>

 #include <asm/cacheflush.h>

 #undef DEBUG

 #undef STATS
 #ifdef STATS
 #define DO_STATS(X) do { X ; } while (0)
 #else
 #define DO_STATS(X) do { } while (0)
 #endif

 /* ************************************************** */

 struct safe_buffer {
 	struct list_head node;

 	/* original request */
 	void		*ptr;
 	size_t		size;
 	int		direction;

 	/* safe buffer info */
 	struct dma_pool *pool;
 	void		*safe;
 	dma_addr_t	safe_dma_addr;
 };

 struct dmabounce_device_info {
 	struct list_head node;

 	struct device *dev;
 	struct dma_pool *small_buffer_pool;
 	struct dma_pool *large_buffer_pool;
 	struct list_head safe_buffers;
 	unsigned long small_buffer_size, large_buffer_size;
 #ifdef STATS
 	unsigned long sbp_allocs;
 	unsigned long lbp_allocs;
 	unsigned long total_allocs;
 	unsigned long map_op_count;
 	unsigned long bounce_count;
 #endif
 };

 static LIST_HEAD(dmabounce_devs);

 #ifdef STATS
 static void print_alloc_stats(struct dmabounce_device_info *device_info)
 {
 	printk(KERN_INFO
 		"%s: dmabounce: sbp: %lu, lbp: %lu, other: %lu, total: %lu\n",
 		device_info->dev->bus_id,
 		device_info->sbp_allocs, device_info->lbp_allocs,
 		device_info->total_allocs - device_info->sbp_allocs -
 			device_info->lbp_allocs,
 		device_info->total_allocs);
 }
 #endif

 /* find the given device in the dmabounce device list */
 static inline struct dmabounce_device_info *
 find_dmabounce_dev(struct device *dev)
 {
 	struct dmabounce_device_info *d;

 	list_for_each_entry(d, &dmabounce_devs, node)
 		if (d->dev == dev)
 			return d;

 	return NULL;
 }


 /* allocate a 'safe' buffer and keep track of it */
 static inline struct safe_buffer *
 alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
 			size_t size, enum dma_data_direction dir)
 {
 	struct safe_buffer *buf;
 	struct dma_pool *pool;
 	struct device *dev = device_info->dev;
 	void *safe;
 	dma_addr_t safe_dma_addr;

 	dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
 		__func__, ptr, size, dir);

 	DO_STATS ( device_info->total_allocs++ );

 	buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
 	if (buf == NULL) {
 		dev_warn(dev, "%s: kmalloc failed\n", __func__);
 		return NULL;
 	}

 	if (size <= device_info->small_buffer_size) {
 		pool = device_info->small_buffer_pool;
 		safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

 		DO_STATS ( device_info->sbp_allocs++ );
 	} else if (size <= device_info->large_buffer_size) {
 		pool = device_info->large_buffer_pool;
 		safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

 		DO_STATS ( device_info->lbp_allocs++ );
 	} else {
 		pool = NULL;
 		safe = dma_alloc_coherent(dev, size, &safe_dma_addr, GFP_ATOMIC);
 	}

 	if (safe == NULL) {
 		dev_warn(device_info->dev,
 			"%s: could not alloc dma memory (size=%d)\n",
 		       __func__, size);
 		kfree(buf);
 		return NULL;
 	}

 #ifdef STATS
 	if (device_info->total_allocs % 1000 == 0)
 		print_alloc_stats(device_info);
 #endif

 	buf->ptr = ptr;
 	buf->size = size;
 	buf->direction = dir;
 	buf->pool = pool;
 	buf->safe = safe;
 	buf->safe_dma_addr = safe_dma_addr;

 	list_add(&buf->node, &device_info->safe_buffers);

 	return buf;
 }

 /* determine if a buffer is from our "safe" pool */
 static inline struct safe_buffer *
 find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
 {
 	struct safe_buffer *b;

 	list_for_each_entry(b, &device_info->safe_buffers, node)
 		if (b->safe_dma_addr == safe_dma_addr)
 			return b;

 	return NULL;
 }

 static inline void
 free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
 {
 	dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

 	list_del(&buf->node);

 	if (buf->pool)
 		dma_pool_free(buf->pool, buf->safe, buf->safe_dma_addr);
 	else
 		dma_free_coherent(device_info->dev, buf->size, buf->safe,
 				    buf->safe_dma_addr);

 	kfree(buf);
 }

 /* ************************************************** */

 #ifdef STATS

 static void print_map_stats(struct dmabounce_device_info *device_info)
 {
 	printk(KERN_INFO
 		"%s: dmabounce: map_op_count=%lu, bounce_count=%lu\n",
 		device_info->dev->bus_id,
 		device_info->map_op_count, device_info->bounce_count);
 }
 #endif

 static inline dma_addr_t
 map_single(struct device *dev, void *ptr, size_t size,
 		enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 	dma_addr_t dma_addr;
 	int needs_bounce = 0;

 	if (device_info)
 		DO_STATS ( device_info->map_op_count++ );

 	dma_addr = virt_to_dma(dev, ptr);

 	if (dev->dma_mask) {
 		unsigned long mask = *dev->dma_mask;
 		unsigned long limit;

 		limit = (mask + 1) & ~mask;
 		if (limit && size > limit) {
 			dev_err(dev, "DMA mapping too big (requested %#x "
 				"mask %#Lx)\n", size, *dev->dma_mask);
 			return ~0;
 		}

 		/*
 		 * Figure out if we need to bounce from the DMA mask.
 		 */
 		needs_bounce = (dma_addr | (dma_addr + size - 1)) & ~mask;
 	}

 	if (device_info && (needs_bounce || dma_needs_bounce(dev, dma_addr, size))) {
 		struct safe_buffer *buf;

 		buf = alloc_safe_buffer(device_info, ptr, size, dir);
 		if (buf == 0) {
 			dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
 			       __func__, ptr);
 			return 0;
 		}

 		dev_dbg(dev,
 			"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 			__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 			buf->safe, (void *) buf->safe_dma_addr);

 		if ((dir == DMA_TO_DEVICE) ||
 		    (dir == DMA_BIDIRECTIONAL)) {
 			dev_dbg(dev, "%s: copy unsafe %p to safe %p, size %d\n",
 				__func__, ptr, buf->safe, size);
 			memcpy(buf->safe, ptr, size);
 		}
 		consistent_sync(buf->safe, size, dir);

 		dma_addr = buf->safe_dma_addr;
 	} else {
 		consistent_sync(ptr, size, dir);
 	}

 	return dma_addr;
 }

 static inline void
 unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 		enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 	struct safe_buffer *buf = NULL;

 	/*
 	 * Trying to unmap an invalid mapping
 	 */
 	if (dma_addr == ~0) {
 		dev_err(dev, "Trying to unmap invalid mapping\n");
 		return;
 	}

 	if (device_info)
 		buf = find_safe_buffer(device_info, dma_addr);

 	if (buf) {
 		BUG_ON(buf->size != size);

 		dev_dbg(dev,
 			"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 			__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 			buf->safe, (void *) buf->safe_dma_addr);

 		DO_STATS ( device_info->bounce_count++ );

 		if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
 			unsigned long ptr;

 			dev_dbg(dev,
 				"%s: copy back safe %p to unsafe %p size %d\n",
 				__func__, buf->safe, buf->ptr, size);
 			memcpy(buf->ptr, buf->safe, size);

 			/*
 			 * DMA buffers must have the same cache properties
 			 * as if they were really used for DMA - which means
 			 * data must be written back to RAM.  Note that
 			 * we don't use dmac_flush_range() here for the
 			 * bidirectional case because we know the cache
 			 * lines will be coherent with the data written.
 			 */
 			ptr = (unsigned long)buf->ptr;
 			dmac_clean_range(ptr, ptr + size);
 		}
 		free_safe_buffer(device_info, buf);
 	}
 }

 static inline void
 sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 		enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 	struct safe_buffer *buf = NULL;

 	if (device_info)
 		buf = find_safe_buffer(device_info, dma_addr);

 	if (buf) {
 		/*
 		 * Both of these checks from original code need to be
 		 * commented out b/c some drivers rely on the following:
 		 *
 		 * 1) Drivers may map a large chunk of memory into DMA space
 		 *    but only sync a small portion of it. Good example is
 		 *    allocating a large buffer, mapping it, and then
 		 *    breaking it up into small descriptors. No point
 		 *    in syncing the whole buffer if you only have to
 		 *    touch one descriptor.
 		 *
 		 * 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
 		 *    usually only synced in one dir at a time.
 		 *
 		 * See drivers/net/eepro100.c for examples of both cases.
 		 *
 		 * -ds
 		 *
 		 * BUG_ON(buf->size != size);
 		 * BUG_ON(buf->direction != dir);
 		 */

 		dev_dbg(dev,
 			"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 			__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 			buf->safe, (void *) buf->safe_dma_addr);

 		DO_STATS ( device_info->bounce_count++ );

 		switch (dir) {
 		case DMA_FROM_DEVICE:
 			dev_dbg(dev,
 				"%s: copy back safe %p to unsafe %p size %d\n",
 				__func__, buf->safe, buf->ptr, size);
 			memcpy(buf->ptr, buf->safe, size);
 			break;
 		case DMA_TO_DEVICE:
 			dev_dbg(dev,
 				"%s: copy out unsafe %p to safe %p, size %d\n",
 				__func__,buf->ptr, buf->safe, size);
 			memcpy(buf->safe, buf->ptr, size);
 			break;
 		case DMA_BIDIRECTIONAL:
 			BUG();	/* is this allowed?  what does it mean? */
 		default:
 			BUG();
 		}
 		consistent_sync(buf->safe, size, dir);
 	} else {
 		consistent_sync(dma_to_virt(dev, dma_addr), size, dir);
 	}
 }

 /* ************************************************** */

 /*
  * see if a buffer address is in an 'unsafe' range.  if it is
  * allocate a 'safe' buffer and copy the unsafe buffer into it.
  * substitute the safe buffer for the unsafe one.
  * (basically move the buffer from an unsafe area to a safe one)
  */
 dma_addr_t
 dma_map_single(struct device *dev, void *ptr, size_t size,
 		enum dma_data_direction dir)
 {
 	unsigned long flags;
 	dma_addr_t dma_addr;

 	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 		__func__, ptr, size, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	dma_addr = map_single(dev, ptr, size, dir);

 	local_irq_restore(flags);

 	return dma_addr;
 }

 /*
  * see if a mapped address was really a "safe" buffer and if so, copy
  * the data from the safe buffer back to the unsafe buffer and free up
  * the safe buffer.  (basically return things back to the way they
  * should be)
  */

 void
 dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 			enum dma_data_direction dir)
 {
 	unsigned long flags;

 	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 		__func__, (void *) dma_addr, size, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	unmap_single(dev, dma_addr, size, dir);

 	local_irq_restore(flags);
 }

 int
 dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		enum dma_data_direction dir)
 {
 	unsigned long flags;
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	for (i = 0; i < nents; i++, sg++) {
 		struct page *page = sg->page;
 		unsigned int offset = sg->offset;
 		unsigned int length = sg->length;
 		void *ptr = page_address(page) + offset;

 		sg->dma_address =
 			map_single(dev, ptr, length, dir);
 	}

 	local_irq_restore(flags);

 	return nents;
 }

 void
 dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 		enum dma_data_direction dir)
 {
 	unsigned long flags;
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		unmap_single(dev, dma_addr, length, dir);
 	}

 	local_irq_restore(flags);
 }

 void
 dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size,
 				enum dma_data_direction dir)
 {
 	unsigned long flags;

 	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 		__func__, (void *) dma_addr, size, dir);

 	local_irq_save(flags);

 	sync_single(dev, dma_addr, size, dir);

 	local_irq_restore(flags);
 }

 void
 dma_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size,
 				enum dma_data_direction dir)
 {
 	unsigned long flags;

 	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 		__func__, (void *) dma_addr, size, dir);

 	local_irq_save(flags);

 	sync_single(dev, dma_addr, size, dir);

 	local_irq_restore(flags);
 }

 void
 dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
 			enum dma_data_direction dir)
 {
 	unsigned long flags;
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		sync_single(dev, dma_addr, length, dir);
 	}

 	local_irq_restore(flags);
 }

 void
 dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
 			enum dma_data_direction dir)
 {
 	unsigned long flags;
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	local_irq_save(flags);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		sync_single(dev, dma_addr, length, dir);
 	}

 	local_irq_restore(flags);
 }

 int
 dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
 			unsigned long large_buffer_size)
 {
 	struct dmabounce_device_info *device_info;

 	device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
 	if (!device_info) {
 		printk(KERN_ERR
 			"Could not allocated dmabounce_device_info for %s",
 			dev->bus_id);
 		return -ENOMEM;
 	}

 	device_info->small_buffer_pool =
 		dma_pool_create("small_dmabounce_pool",
 				dev,
 				small_buffer_size,
 				0 /* byte alignment */,
 				0 /* no page-crossing issues */);
 	if (!device_info->small_buffer_pool) {
 		printk(KERN_ERR
 			"dmabounce: could not allocate small DMA pool for %s\n",
 			dev->bus_id);
 		kfree(device_info);
 		return -ENOMEM;
 	}

 	if (large_buffer_size) {
 		device_info->large_buffer_pool =
 			dma_pool_create("large_dmabounce_pool",
 					dev,
 					large_buffer_size,
 					0 /* byte alignment */,
 					0 /* no page-crossing issues */);
 		if (!device_info->large_buffer_pool) {
 		printk(KERN_ERR
 			"dmabounce: could not allocate large DMA pool for %s\n",
 			dev->bus_id);
 			dma_pool_destroy(device_info->small_buffer_pool);

 			return -ENOMEM;
 		}
 	}

 	device_info->dev = dev;
 	device_info->small_buffer_size = small_buffer_size;
 	device_info->large_buffer_size = large_buffer_size;
 	INIT_LIST_HEAD(&device_info->safe_buffers);

 #ifdef STATS
 	device_info->sbp_allocs = 0;
 	device_info->lbp_allocs = 0;
 	device_info->total_allocs = 0;
 	device_info->map_op_count = 0;
 	device_info->bounce_count = 0;
 #endif

 	list_add(&device_info->node, &dmabounce_devs);

 	printk(KERN_INFO "dmabounce: registered device %s on %s bus\n",
 		dev->bus_id, dev->bus->name);

 	return 0;
 }

 void
 dmabounce_unregister_dev(struct device *dev)
 {
 	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);

 	if (!device_info) {
 		printk(KERN_WARNING
 			"%s: Never registered with dmabounce but attempting" \
 			"to unregister!\n", dev->bus_id);
 		return;
 	}

 	if (!list_empty(&device_info->safe_buffers)) {
 		printk(KERN_ERR
 			"%s: Removing from dmabounce with pending buffers!\n",
 			dev->bus_id);
 		BUG();
 	}

 	if (device_info->small_buffer_pool)
 		dma_pool_destroy(device_info->small_buffer_pool);
 	if (device_info->large_buffer_pool)
 		dma_pool_destroy(device_info->large_buffer_pool);

 #ifdef STATS
 	print_alloc_stats(device_info);
 	print_map_stats(device_info);
 #endif

 	list_del(&device_info->node);

 	kfree(device_info);

 	printk(KERN_INFO "dmabounce: device %s on %s bus unregistered\n",
 		dev->bus_id, dev->bus->name);
 }


 EXPORT_SYMBOL(dma_map_single);
 EXPORT_SYMBOL(dma_unmap_single);
 EXPORT_SYMBOL(dma_map_sg);
 EXPORT_SYMBOL(dma_unmap_sg);
 EXPORT_SYMBOL(dma_sync_single);
 EXPORT_SYMBOL(dma_sync_sg);
 EXPORT_SYMBOL(dmabounce_register_dev);
 EXPORT_SYMBOL(dmabounce_unregister_dev);

 MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
 MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
 MODULE_LICENSE("GPL");
	/*
	* arch/arm/common/dmabounce.c
	*
	* Special dma_{map/unmap/dma_sync}_* routines for systems that have
	* limited DMA windows. These functions utilize bounce buffers to
	* copy data to/from buffers located outside the DMA region. This
	* only works for systems in which DMA memory is at the bottom of
	* RAM and the remainder of memory is at the top an the DMA memory
	* can be marked as ZONE_DMA. Anything beyond that such as discontigous
	* DMA windows will require custom implementations that reserve memory
	* areas at early bootup.
	*
	* Original version by Brad Parker (brad@heeltoe.com)
	* Re-written by Christopher Hoover <ch@murgatroid.com>
	* Made generic by Deepak Saxena <dsaxena@plexity.net>
	*
	* Copyright (C) 2002 Hewlett Packard Company.
	* Copyright (C) 2004 MontaVista Software, Inc.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* version 2 as published by the Free Software Foundation.
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/device.h>
	#include <linux/dma-mapping.h>
	#include <linux/dmapool.h>
	#include <linux/list.h>

	#include <asm/cacheflush.h>

	#undef DEBUG

	#undef STATS
	#ifdef STATS
	#define DO_STATS(X) do { X ; } while (0)
	#else
	#define DO_STATS(X) do { } while (0)
	#endif

	/* ************************************************** */

	struct safe_buffer {
	struct list_head node;

	/* original request */
	void *ptr;
	size_t size;
	int direction;

	/* safe buffer info */
	struct dma_pool *pool;
	void *safe;
	dma_addr_t safe_dma_addr;
	};

	struct dmabounce_device_info {
	struct list_head node;

	struct device *dev;
	struct dma_pool *small_buffer_pool;
	struct dma_pool *large_buffer_pool;
	struct list_head safe_buffers;
	unsigned long small_buffer_size, large_buffer_size;
	#ifdef STATS
	unsigned long sbp_allocs;
	unsigned long lbp_allocs;
	unsigned long total_allocs;
	unsigned long map_op_count;
	unsigned long bounce_count;
	#endif
	};

	static LIST_HEAD(dmabounce_devs);

	#ifdef STATS
	static void print_alloc_stats(struct dmabounce_device_info *device_info)
	{
	printk(KERN_INFO
	"%s: dmabounce: sbp: %lu, lbp: %lu, other: %lu, total: %lu\n",
	device_info->dev->bus_id,
	device_info->sbp_allocs, device_info->lbp_allocs,
	device_info->total_allocs - device_info->sbp_allocs -
	device_info->lbp_allocs,
	device_info->total_allocs);
	}
	#endif

	/* find the given device in the dmabounce device list */
	static inline struct dmabounce_device_info *
	find_dmabounce_dev(struct device *dev)
	{
	struct dmabounce_device_info *d;

	list_for_each_entry(d, &dmabounce_devs, node)
	if (d->dev == dev)
	return d;

	return NULL;
	}


	/* allocate a 'safe' buffer and keep track of it */
	static inline struct safe_buffer *
	alloc_safe_buffer(struct dmabounce_device_info device_info, void ptr,
	size_t size, enum dma_data_direction dir)
	{
	struct safe_buffer *buf;
	struct dma_pool *pool;
	struct device *dev = device_info->dev;
	void *safe;
	dma_addr_t safe_dma_addr;

	dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
	__func__, ptr, size, dir);

	DO_STATS ( device_info->total_allocs++ );

	buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
	if (buf == NULL) {
	dev_warn(dev, "%s: kmalloc failed\n", __func__);
	return NULL;
	}

	if (size <= device_info->small_buffer_size) {
	pool = device_info->small_buffer_pool;
	safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

	DO_STATS ( device_info->sbp_allocs++ );
	} else if (size <= device_info->large_buffer_size) {
	pool = device_info->large_buffer_pool;
	safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

	DO_STATS ( device_info->lbp_allocs++ );
	} else {
	pool = NULL;
	safe = dma_alloc_coherent(dev, size, &safe_dma_addr, GFP_ATOMIC);
	}

	if (safe == NULL) {
	dev_warn(device_info->dev,
	"%s: could not alloc dma memory (size=%d)\n",
	__func__, size);
	kfree(buf);
	return NULL;
	}

	#ifdef STATS
	if (device_info->total_allocs % 1000 == 0)
	print_alloc_stats(device_info);
	#endif

	buf->ptr = ptr;
	buf->size = size;
	buf->direction = dir;
	buf->pool = pool;
	buf->safe = safe;
	buf->safe_dma_addr = safe_dma_addr;

	list_add(&buf->node, &device_info->safe_buffers);

	return buf;
	}

	/* determine if a buffer is from our "safe" pool */
	static inline struct safe_buffer *
	find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
	{
	struct safe_buffer *b;

	list_for_each_entry(b, &device_info->safe_buffers, node)
	if (b->safe_dma_addr == safe_dma_addr)
	return b;

	return NULL;
	}

	static inline void
	free_safe_buffer(struct dmabounce_device_info device_info, struct safe_buffer buf)
	{
	dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

	list_del(&buf->node);

	if (buf->pool)
	dma_pool_free(buf->pool, buf->safe, buf->safe_dma_addr);
	else
	dma_free_coherent(device_info->dev, buf->size, buf->safe,
	buf->safe_dma_addr);

	kfree(buf);
	}

	/* ************************************************** */

	#ifdef STATS

	static void print_map_stats(struct dmabounce_device_info *device_info)
	{
	printk(KERN_INFO
	"%s: dmabounce: map_op_count=%lu, bounce_count=%lu\n",
	device_info->dev->bus_id,
	device_info->map_op_count, device_info->bounce_count);
	}
	#endif

	static inline dma_addr_t
	map_single(struct device dev, void ptr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
	dma_addr_t dma_addr;
	int needs_bounce = 0;

	if (device_info)
	DO_STATS ( device_info->map_op_count++ );

	dma_addr = virt_to_dma(dev, ptr);

	if (dev->dma_mask) {
	unsigned long mask = *dev->dma_mask;
	unsigned long limit;

	limit = (mask + 1) & ~mask;
	if (limit && size > limit) {
	dev_err(dev, "DMA mapping too big (requested %#x "
	"mask %#Lx)\n", size, *dev->dma_mask);
	return ~0;
	}

	/*
	* Figure out if we need to bounce from the DMA mask.
	*/
	needs_bounce = (dma_addr \| (dma_addr + size - 1)) & ~mask;
	}

	if (device_info && (needs_bounce \|\| dma_needs_bounce(dev, dma_addr, size))) {
	struct safe_buffer *buf;

	buf = alloc_safe_buffer(device_info, ptr, size, dir);
	if (buf == 0) {
	dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
	__func__, ptr);
	return 0;
	}

	dev_dbg(dev,
	"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
	__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
	buf->safe, (void *) buf->safe_dma_addr);

	if ((dir == DMA_TO_DEVICE) \|\|
	(dir == DMA_BIDIRECTIONAL)) {
	dev_dbg(dev, "%s: copy unsafe %p to safe %p, size %d\n",
	__func__, ptr, buf->safe, size);
	memcpy(buf->safe, ptr, size);
	}
	consistent_sync(buf->safe, size, dir);

	dma_addr = buf->safe_dma_addr;
	} else {
	consistent_sync(ptr, size, dir);
	}

	return dma_addr;
	}

	static inline void
	unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
	struct safe_buffer *buf = NULL;

	/*
	* Trying to unmap an invalid mapping
	*/
	if (dma_addr == ~0) {
	dev_err(dev, "Trying to unmap invalid mapping\n");
	return;
	}

	if (device_info)
	buf = find_safe_buffer(device_info, dma_addr);

	if (buf) {
	BUG_ON(buf->size != size);

	dev_dbg(dev,
	"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
	__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
	buf->safe, (void *) buf->safe_dma_addr);

	DO_STATS ( device_info->bounce_count++ );

	if (dir == DMA_FROM_DEVICE \|\| dir == DMA_BIDIRECTIONAL) {
	unsigned long ptr;

	dev_dbg(dev,
	"%s: copy back safe %p to unsafe %p size %d\n",
	__func__, buf->safe, buf->ptr, size);
	memcpy(buf->ptr, buf->safe, size);

	/*
	* DMA buffers must have the same cache properties
	* as if they were really used for DMA - which means
	* data must be written back to RAM. Note that
	* we don't use dmac_flush_range() here for the
	* bidirectional case because we know the cache
	* lines will be coherent with the data written.
	*/
	ptr = (unsigned long)buf->ptr;
	dmac_clean_range(ptr, ptr + size);
	}
	free_safe_buffer(device_info, buf);
	}
	}

	static inline void
	sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
	struct safe_buffer *buf = NULL;

	if (device_info)
	buf = find_safe_buffer(device_info, dma_addr);

	if (buf) {
	/*
	* Both of these checks from original code need to be
	* commented out b/c some drivers rely on the following:
	*
	* 1) Drivers may map a large chunk of memory into DMA space
	* but only sync a small portion of it. Good example is
	* allocating a large buffer, mapping it, and then
	* breaking it up into small descriptors. No point
	* in syncing the whole buffer if you only have to
	* touch one descriptor.
	*
	* 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
	* usually only synced in one dir at a time.
	*
	* See drivers/net/eepro100.c for examples of both cases.
	*
	* -ds
	*
	* BUG_ON(buf->size != size);
	* BUG_ON(buf->direction != dir);
	*/

	dev_dbg(dev,
	"%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
	__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
	buf->safe, (void *) buf->safe_dma_addr);

	DO_STATS ( device_info->bounce_count++ );

	switch (dir) {
	case DMA_FROM_DEVICE:
	dev_dbg(dev,
	"%s: copy back safe %p to unsafe %p size %d\n",
	__func__, buf->safe, buf->ptr, size);
	memcpy(buf->ptr, buf->safe, size);
	break;
	case DMA_TO_DEVICE:
	dev_dbg(dev,
	"%s: copy out unsafe %p to safe %p, size %d\n",
	__func__,buf->ptr, buf->safe, size);
	memcpy(buf->safe, buf->ptr, size);
	break;
	case DMA_BIDIRECTIONAL:
	BUG(); /* is this allowed? what does it mean? */
	default:
	BUG();
	}
	consistent_sync(buf->safe, size, dir);
	} else {
	consistent_sync(dma_to_virt(dev, dma_addr), size, dir);
	}
	}

	/* ************************************************** */

	/*
	* see if a buffer address is in an 'unsafe' range. if it is
	* allocate a 'safe' buffer and copy the unsafe buffer into it.
	* substitute the safe buffer for the unsafe one.
	* (basically move the buffer from an unsafe area to a safe one)
	*/
	dma_addr_t
	dma_map_single(struct device dev, void ptr, size_t size,
	enum dma_data_direction dir)
	{
	unsigned long flags;
	dma_addr_t dma_addr;

	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
	__func__, ptr, size, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	dma_addr = map_single(dev, ptr, size, dir);

	local_irq_restore(flags);

	return dma_addr;
	}

	/*
	* see if a mapped address was really a "safe" buffer and if so, copy
	* the data from the safe buffer back to the unsafe buffer and free up
	* the safe buffer. (basically return things back to the way they
	* should be)
	*/

	void
	dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	unsigned long flags;

	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
	__func__, (void *) dma_addr, size, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	unmap_single(dev, dma_addr, size, dir);

	local_irq_restore(flags);
	}

	int
	dma_map_sg(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	unsigned long flags;
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	for (i = 0; i < nents; i++, sg++) {
	struct page *page = sg->page;
	unsigned int offset = sg->offset;
	unsigned int length = sg->length;
	void *ptr = page_address(page) + offset;

	sg->dma_address =
	map_single(dev, ptr, length, dir);
	}

	local_irq_restore(flags);

	return nents;
	}

	void
	dma_unmap_sg(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	unsigned long flags;
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	unmap_single(dev, dma_addr, length, dir);
	}

	local_irq_restore(flags);
	}

	void
	dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	unsigned long flags;

	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
	__func__, (void *) dma_addr, size, dir);

	local_irq_save(flags);

	sync_single(dev, dma_addr, size, dir);

	local_irq_restore(flags);
	}

	void
	dma_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	unsigned long flags;

	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
	__func__, (void *) dma_addr, size, dir);

	local_irq_save(flags);

	sync_single(dev, dma_addr, size, dir);

	local_irq_restore(flags);
	}

	void
	dma_sync_sg_for_cpu(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	unsigned long flags;
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	sync_single(dev, dma_addr, length, dir);
	}

	local_irq_restore(flags);
	}

	void
	dma_sync_sg_for_device(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	unsigned long flags;
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	local_irq_save(flags);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	sync_single(dev, dma_addr, length, dir);
	}

	local_irq_restore(flags);
	}

	int
	dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
	unsigned long large_buffer_size)
	{
	struct dmabounce_device_info *device_info;

	device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
	if (!device_info) {
	printk(KERN_ERR
	"Could not allocated dmabounce_device_info for %s",
	dev->bus_id);
	return -ENOMEM;
	}

	device_info->small_buffer_pool =
	dma_pool_create("small_dmabounce_pool",
	dev,
	small_buffer_size,
	0 /* byte alignment */,
	0 /* no page-crossing issues */);
	if (!device_info->small_buffer_pool) {
	printk(KERN_ERR
	"dmabounce: could not allocate small DMA pool for %s\n",
	dev->bus_id);
	kfree(device_info);
	return -ENOMEM;
	}

	if (large_buffer_size) {
	device_info->large_buffer_pool =
	dma_pool_create("large_dmabounce_pool",
	dev,
	large_buffer_size,
	0 /* byte alignment */,
	0 /* no page-crossing issues */);
	if (!device_info->large_buffer_pool) {
	printk(KERN_ERR
	"dmabounce: could not allocate large DMA pool for %s\n",
	dev->bus_id);
	dma_pool_destroy(device_info->small_buffer_pool);

	return -ENOMEM;
	}
	}

	device_info->dev = dev;
	device_info->small_buffer_size = small_buffer_size;
	device_info->large_buffer_size = large_buffer_size;
	INIT_LIST_HEAD(&device_info->safe_buffers);

	#ifdef STATS
	device_info->sbp_allocs = 0;
	device_info->lbp_allocs = 0;
	device_info->total_allocs = 0;
	device_info->map_op_count = 0;
	device_info->bounce_count = 0;
	#endif

	list_add(&device_info->node, &dmabounce_devs);

	printk(KERN_INFO "dmabounce: registered device %s on %s bus\n",
	dev->bus_id, dev->bus->name);

	return 0;
	}

	void
	dmabounce_unregister_dev(struct device *dev)
	{
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);

	if (!device_info) {
	printk(KERN_WARNING
	"%s: Never registered with dmabounce but attempting" \
	"to unregister!\n", dev->bus_id);
	return;
	}

	if (!list_empty(&device_info->safe_buffers)) {
	printk(KERN_ERR
	"%s: Removing from dmabounce with pending buffers!\n",
	dev->bus_id);
	BUG();
	}

	if (device_info->small_buffer_pool)
	dma_pool_destroy(device_info->small_buffer_pool);
	if (device_info->large_buffer_pool)
	dma_pool_destroy(device_info->large_buffer_pool);

	#ifdef STATS
	print_alloc_stats(device_info);
	print_map_stats(device_info);
	#endif

	list_del(&device_info->node);

	kfree(device_info);

	printk(KERN_INFO "dmabounce: device %s on %s bus unregistered\n",
	dev->bus_id, dev->bus->name);
	}


	EXPORT_SYMBOL(dma_map_single);
	EXPORT_SYMBOL(dma_unmap_single);
	EXPORT_SYMBOL(dma_map_sg);
	EXPORT_SYMBOL(dma_unmap_sg);
	EXPORT_SYMBOL(dma_sync_single);
	EXPORT_SYMBOL(dma_sync_sg);
	EXPORT_SYMBOL(dmabounce_register_dev);
	EXPORT_SYMBOL(dmabounce_unregister_dev);

	MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
	MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
	MODULE_LICENSE("GPL");